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import java.util.Scanner;public class CaesarCipher { // Moves every letter k places forward in the alphabet, wrapping Z back to A static String shift(String str, int k) { String result = ""; for (char c : str.toCharArray()) { if (Character.isUpperCase(c)) c = (char) ('A' + (c - 'A' + k) % 26); else if (Character.isLowerCase(c)) c = (char) ('a' + (c - 'a' + k) % 26); result += c; } return result; } public static void main(String[] args) { Scanner sc = new Scanner(System.in); System.out.print("Enter any String: "); String str = sc.nextLine(); System.out.print("\nEnter the Key: "); int key = sc.nextInt() % 26; String encrypted = shift(str, key); System.out.println("\nEncrypted String is: " + encrypted); System.out.println("\nDecrypted String is: " + shift(encrypted, 26 - key)); System.out.println(); }}_______3.bimport java.util.Scanner;public class SubstitutionCipher { public static void main(String[] args) { String a = "abcdefghijklmnopqrstuvwxyzH"; String b = "zyxwvutsrqponmlkjihgfedcbaS"; System.out.print("Enter any string: "); String str = new Scanner(System.in).nextLine(); String encrypted = ""; for (char c : str.toCharArray()) encrypted += b.charAt(a.indexOf(c)); // partner letter from b System.out.println("The encrypted data is: " + encrypted); }}_________des algoimport java.util.Base64;import java.util.Scanner;import javax.crypto.Cipher;import javax.crypto.SecretKey;import javax.crypto.SecretKeyFactory;import javax.crypto.spec.DESedeKeySpec;public class DES { public static void main(String[] args) throws Exception { System.out.print("Enter the string: "); String text = new Scanner(System.in).nextLine(); byte[] keyBytes = "ThisIsSecretEncryptionKey".getBytes("UTF8"); SecretKeyFactory factory = SecretKeyFactory.getInstance("DESede"); SecretKey key = factory.generateSecret(new DESedeKeySpec(keyBytes)); Cipher cipher = Cipher.getInstance("DESede"); cipher.init(Cipher.ENCRYPT_MODE, key); byte[] encryptedBytes = cipher.doFinal(text.getBytes("UTF8")); String encrypted = Base64.getEncoder().encodeToString(encryptedBytes); cipher.init(Cipher.DECRYPT_MODE, key); byte[] decryptedBytes = cipher.doFinal(Base64.getDecoder().decode(encrypted)); String decrypted = new String(decryptedBytes, "UTF8"); System.out.println("\nString To Encrypt : " + text); System.out.println("Encrypted Value : " + encrypted); System.out.println("Decrypted Value : " + decrypted); }}_______ blowfishimport java.util.Base64;import java.util.Scanner;import javax.crypto.Cipher;import javax.crypto.KeyGenerator;public class BlowFish { public static void main(String[] args) throws Exception { KeyGenerator keyGenerator = KeyGenerator.getInstance("Blowfish"); keyGenerator.init(128); Cipher cipher = Cipher.getInstance("Blowfish/CFB/NoPadding"); cipher.init(Cipher.ENCRYPT_MODE, keyGenerator.generateKey()); System.out.println("Initialization Vector of the Cipher: " + Base64.getEncoder().encodeToString(cipher.getIV())); System.out.print("Enter text to encrypt: "); String text = new Scanner(System.in).nextLine(); byte[] encrypted = cipher.doFinal(text.getBytes()); System.out.println("Encrypted Text: " + Base64.getEncoder().encodeToString(encrypted)); }}_______rij agloimport java.util.Scanner;import javax.crypto.Cipher;import javax.crypto.KeyGenerator;import javax.crypto.SecretKey;public class AES { static String asHex(byte[] bytes) { String hex = ""; for (byte b : bytes) hex += String.format("%02x", b); return hex; } public static void main(String[] args) throws Exception { System.out.print("Enter the data to be encrypted: "); String message = new Scanner(System.in).nextLine(); KeyGenerator kgen = KeyGenerator.getInstance("AES"); kgen.init(128); SecretKey key = kgen.generateKey(); Cipher cipher = Cipher.getInstance("AES"); cipher.init(Cipher.ENCRYPT_MODE, key); byte[] encrypted = cipher.doFinal(message.getBytes("UTF-8")); System.out.println("Encrypted string: " + asHex(encrypted)); cipher.init(Cipher.DECRYPT_MODE, key); byte[] original = cipher.doFinal(encrypted); System.out.println("Original string: " + new String(original, "UTF-8")); System.out.println("Original data in hexadecimal: " + asHex(original)); }}_____rc4import java.util.Scanner;import javax.crypto.Cipher;import javax.crypto.KeyGenerator;import javax.crypto.SecretKey;public class BlowFishCipher { public static void main(String[] args) throws Exception { SecretKey key = KeyGenerator.getInstance("Blowfish").generateKey(); Cipher cipher = Cipher.getInstance("Blowfish"); System.out.print("Input your message: "); String text = new Scanner(System.in).nextLine(); cipher.init(Cipher.ENCRYPT_MODE, key); byte[] encrypted = cipher.doFinal(text.getBytes("UTF-8")); String hex = ""; for (byte b : encrypted) hex += String.format("%02X", b); cipher.init(Cipher.DECRYPT_MODE, key); byte[] decrypted = cipher.doFinal(encrypted); System.out.println("Encrypted text: " + hex); System.out.println("Decrypted text: " + new String(decrypted, "UTF-8")); }}________rsaimport java.math.BigInteger;import java.util.Random;import java.util.Scanner;public class RSA { public static void main(String[] args) { Scanner sc = new Scanner(System.in); System.out.print("Enter a Prime number: "); BigInteger p = sc.nextBigInteger(); System.out.print("Enter another prime number: "); BigInteger q = sc.nextBigInteger(); BigInteger n = p.multiply(q); BigInteger one = BigInteger.ONE; BigInteger phi = p.subtract(one).multiply(q.subtract(one)); // Pick a random e (greater than 2) with gcd(e, phi) = 1 Random r = new Random(); BigInteger e; do { e = BigInteger.valueOf(r.nextInt(phi.intValue() - 1)); } while (e.intValue() <= 2 || !phi.gcd(e).equals(BigInteger.ONE)); BigInteger d = e.modInverse(phi); // d x e = 1 (mod phi) System.out.println("Encryption keys are: " + e + ", " + n); System.out.println("Decryption keys are: " + d + ", " + n); }}____hellmanimport java.math.BigInteger;import java.security.KeyFactory;import java.security.KeyPairGenerator;import java.security.SecureRandom;import javax.crypto.spec.DHParameterSpec;import javax.crypto.spec.DHPublicKeySpec;public class DiffeHellman { // Generates a key pair and prints its public key static void printPublicKey(KeyPairGenerator kpg) throws Exception { DHPublicKeySpec kspec = KeyFactory.getInstance("DiffieHellman") .getKeySpec(kpg.generateKeyPair().getPublic(), DHPublicKeySpec.class); System.out.println("Public key is: " + kspec); } public static void main(String[] args) throws Exception { KeyPairGenerator kpg = KeyPairGenerator.getInstance("DiffieHellman"); kpg.initialize(512); printPublicKey(kpg); SecureRandom rnd = new SecureRandom(); BigInteger p = BigInteger.probablePrime(512, rnd); BigInteger g = BigInteger.probablePrime(512, rnd); kpg.initialize(new DHParameterSpec(p, g)); System.out.println(); printPublicKey(kpg); }}_____Programimport java.security.MessageDigest;public class SHA1 { public static void main(String[] args) throws Exception { MessageDigest md = MessageDigest.getInstance("SHA1"); System.out.println("Message digest object info: "); System.out.println(" Algorithm = " + md.getAlgorithm()); System.out.println(" Provider = " + md.getProvider()); System.out.println(" ToString = " + md); String[] inputs = { "", "abc", "abcdefghijklmnopqrstuvwxyz" }; for (String input : inputs) { String hex = ""; for (byte b : md.digest(input.getBytes())) hex += String.format("%02X", b); System.out.println("\nSHA1(\"" + input + "\") = " + hex); } System.out.println(); }}____md5import java.security.MessageDigest;public class MD5 { public static void main(String[] args) throws Exception { MessageDigest md = MessageDigest.getInstance("MD5"); System.out.println("Message digest object info: "); System.out.println(" Algorithm = " + md.getAlgorithm()); System.out.println(" Provider = " + md.getProvider()); System.out.println(" ToString = " + md); String[] inputs = { "", "abc", "abcdefghijklmnopqrstuvwxyz" }; for (String input : inputs) { String hex = ""; for (byte b : md.digest(input.getBytes())) hex += String.format("%02X", b); System.out.println("\nMD5(\"" + input + "\") = " + hex); } System.out.println(); }}_______